A gas injection is taken from the sampling line at a specific temperature to determine the composition of the uncondensed gases using a gas chromatography-thermal conductivity detector (GC-TCD). The GC used was HP 5890 Series II Gas Chromatograph with a 60/80 Carboxen-1000, 15× 1/8SS (2.1 mm I.D.) column. Helium is used as the carrier gas with a flowrate of 30 ml/min, and the calibration gases is a mixture of permanent gases which consists of hydrogen (H2), nitrogen (N2), methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2). A volume of 100 l was injected at a single run. The initial oven temperature was held at 35◦C for 5 min, and then ramped up to 225◦C at a rate of 20◦C/min.
Rice husks with a particle size of 355–849 m was used for the experiments. The pyrolysis condition for the primary reactor is 450◦C with a heating rate of 25◦C/min. The secondary reactor, containing the catalyst is kept at a range of 490–540◦C. A nitrogen gas flow of 50 cm3/min is maintained continuously throughout the experiment to purge the system.